Lots of little things...

For the past six months, my MacBook Air has been buggy. For example, the dashboard at the bottom doesn't come up readily. Sometimes I have to move the cursor down there four or five times before it will show.

Also, my yahoo email accounts keep asking for my password even though I put it in correctly. My yahoo mail won't send from my MacBook Air but it sends from my other devices that are set up the same way.

Any suggestions?

Thanks